Silk's sweet spot: untangling the requirements for artificial silk extrusion using a biomimetic approach

Abstract: Up to this date, only a few silk hydrogels were reported to be injectable. Of these, none are truly biomimetic, and are instead comprised of blends with limited amounts of silk. Hence, no truly silk-based hydrogels exist as of today. From the reported injectable matrices, only a few have considered the natural progressive acidification to which silk proteins are exposed before spinning. Adding to that, none has considered the physiological limitations of the active silk-spinners, nor even what is the definition of a suitable extrusion. In this report it is demonstrated that, even though silk spinning is a pultrusion-dominated process, one can achieve a biologically-relevant extrusion of silks that falls within the physiological capacities of the organisms that naturally spin silk. Furthermore, it is reported the existence of a specific concentration of silk where extruded gels reveal characteristics of an ideal injectable matrix.